Small, but Pugnacious: The Pseudocheilinus Wrasses (Full Article)

Author: Bob Fenner

Photographer: Jonathan Truong

Wrasses of the genus Pseudocheilinus impress with their gorgeous colors, but they can become real terrors when coupled with the wrong tankmates.

The wrasses of the genus Pseudocheilinus appear to have much going for them. They are commonly available and stay relatively small, plus they’re good-looking, intelligent fishes. They are shrinking violet terrors, however. While they can be extremely aggressive to tankmates, these labrids are also top contenders for being the poster fish for shyness. Although quite common in their natural ranges, with the exception of P. ocellatus, divers miss seeing them about as much as anxious reef aquarists who keep them. But despite their tendency to be little terrors and their propensity for hiding, these fishes can make engaging, albeit fleetingly seen additions to many types of marine systems.

Natural History

All told, there are seven scientifically described species of Pseudocheilinus. Of these, two hail from restricted ranges and are extremely rare in the trade. In fact, I have yet to come upon P. citrinus (from the Pitcairn Islands to Rarotonga) or P. dispilus (from the Mascarene Islands) in the United States trade. The other five species are often available, however. Their collective distribution covers the mid-Pacific (Hawai‘i and Polynesia, the West Pacific to East Africa’s coast and the Red Sea). These are shallow-water reef fishes, again with the exception of P. ocellatus, which is rarely found in water shallower than 100 feet. They live in and among rocky rubble and its associated attached life.

Available Aquarium Species

Pseudocheilinus evanidus

P. evanidus is usually called the pinstriped or striated wrasse, but I prefer two of its other common names: the disappearing or vanishing wrasse. It grows to a size of only 3 inches. P. evanidus has a wide range covering the Indo-Pacific, including the Red Sea and Hawai‘i.

Pseudocheilinus hexataenia

Called both the six-line and the twelve-line wrasse, P. hexataenia is a feisty but small (growing up to a size of 4 inches) fish that is appropriate for a reef tank. It is distributed in the Indo-Pacific, including the Red Sea.

Pseudocheilinus ocellatus

The deepwater P. ocellatus is known by several common names: the mystery wrasse, the tail-spot wrasse, and the five-bar wrasse. Growing to 4 inches in length, it comes from the west-central Pacific.

Pseudocheilinus octotaenia

A slightly larger fish, P. octotaenia grows to 5½ inches and is known as the eight-lined or twelve-lined wrasse. It comes in two color morphs, one more orange and the other more pinkish in body hue. Its range is the Indo-Pacific, including Hawai‘i.

Pseudocheilinus tetrataenia

Often called the four-line wrasse, P. tetrataenia, like all members of the genus, is best kept one to a tank. It grows 3 inches long and inhabits the west-central Pacific.

Behavior

As noted, these fishes are shy to the point of invisibility, spending their daylight periods skulking about in crevices and caves on the bottom. Although frustrating for an aquarist, this full-time activity serves them well in seeking out their favored food items as well as in avoiding predators.

I should mention that these wrasses sleep in cocoons, not under the sand. They exude body mucus and sleep in a bag-type arrangement similar to many parrotfishes. This is thought to aid in avoiding predators. You may see yours ingesting this mucus on waking in the morning.

A disturbing behavior that should be guarded against is their tendency for jumping out of systems. These little wrasses can launch themselves up and through small openings. Do make sure you have your top completely screened.

(In)compatibility

All of these wrasses can become agonistic toward other fishes, particularly species that inhabit similar between-rock niches and habitats. Undercrowding, overdecorating, and keen observation are called for here, as always. Unless your system is at least 100 gallons, some 5 to 6 feet in length, fish families like the dottybacks, dartfishes, grammas, Liopropoma, and small clownfishes should be avoided. These fish frequently fall prey to harassment from even smaller individuals of Pseudocheilinus.

Reciprocally, other overly reef-rock territorial fishes can turn the table on these lined wrasses. Hawkfishes, mandarins, lizardfishes, larger and more aggressive wrasses, damsels, and large clownfishes should not share their tanks.

Pseudocheilinus wrasses are reef-safe and leave stinging-celled life be, though you may occasionally find yours picking around sessile invertebrates, looking for the small worms, crustaceans, and the like that they feed on. Very little damage is done by this picking. Small hermits and shrimps (peppermints, cleaners, etc.) may tempt your wrasse, especially while soft bodied during molting. Small snails and small tridacnid clams have been nipped by these species on occasion—possibly in their quest for pyramidellid parasites. Oh, and though they do not harm hard and soft corals, not all cnidarians are safe for the wrasses—Pseudocheilinus have been consumed by sea anemones in captivity.

Can you place more than one specimen in a given display? Perhaps. Ample space is needed, and they should be introduced at the same time. Even then there are no guarantees other than if you only place one that it will get along with itself!

If there are real troubles, you may need to separate the contenders. That task is no fun in a fully set-up reef system, though sometimes leaving the lights off for a few days and rearranging your carefully built rock decor can alleviate aggression. As usual, the onus is upon you to carefully observe and care for your livestock.

Selection

For being such small, reclusive species, the lined wrasses are remarkably good shippers. Look for a bright quality in prospective buys—that they’re alert and looking about for food. Unless the one you’re evaluating for purchase is obviously damaged (split fins are okay), it is likely good to go.

Of the five species, the disappearing and four-line wrasses are by and large easygoing, with the other species, particularly the eight and six-line, tending to be the most antagonistic.

Systems

While these species are typically seen moving about slowly in the wild, they will still get around in all but the largest hobbyist systems. This is why they must not be crowded with other rock-dwelling fish species, including conspecifics and congeners, to prevent aggression. I have seen four- and six-lines kept in volumes of only a few tens of gallons, but they were the only fish present. It is better by far to stock these fishes in larger, full reef settings. Lighting, filtration, and circulation for these wrasses are all reef standard.

I’ve already mentioned these fishes’ penchant for jumping out of their systems. If you leave the top of your tank open, do devise a way of preventing yours from exiting stage up.

Nutrition

In the wild, Pseudocheilinus feed on small invertebrates, mostly worms, crustaceans, and snails found on rock or on the sand near it. In captivity they have proven to be eager acceptors of most all suitably sized meaty foods. The very best arrangement for them is to have both a good deal of live rock in their system to browse on, and a large, vibrant refugium that generates copious quantities of ’pods. I would offer these fish other foods twice a day as well. Copepods, cyclops, and mysids are great choices.

Health

In addition to the common protozoan parasites that most reef fishes are subject to, this genus suffers more than its share of physical traumas. Their habit of launching themselves out of tanks or against the tops of tanks, lights, and into hard surfaces in the tank results in many mouth and eye injuries. One way to fight this trend is to do what you can to slowly (as opposed to all at once) turn on and off lighting, even making provision for some outside light to be on at all times. An additional solution has already been mentioned: Stock them only in large volumes to grant a sense of security and minimize aggression.

Another type of physical injury that occurs often enough to mention is these fishes getting spiked by polychaete (bristle) worms in the course of eating them. If yours appears to have spines sticking out of its mouth or around the face, don’t panic. These generally work themselves out in days to a couple of weeks.

Cryptocaryon and Amyloodinium can be cured by the usual means—pH-adjusted freshwater baths to rid the hosts, then subsequent hospital-tank treatment (with 0.2 to 0.3 ppm free cupric ion) for two to three weeks. Meanwhile, elevated temperature (at 85° to 90°F) in the fallow display tank will speed up the metabolism of the parasites, speeding their deaths in the absence of food (host fishes).

But altogether, these fishes are hardy and disease resistant. Some are known to have lived more than a decade in captivity.

Breeding

Like other labrids, Pseudocheilinus spp. are protogynous hermaphrodites, becoming females first, then males. As far as I’ve observed, they live singly once mature, with only brief liaisons between individuals; i.e. they are not haremic species. There are no discernible differences between the sexes, and as far as I’m aware, none of the species has been spawned and reared in captivity.

Small and Charming

The diminutive wrasses of the genus Pseudocheilinus have many admirable qualities aside from their small growth. They are unique, interesting characters that make for endless fun and discussion points once they are trained to come out. Just be sure of the likely compatibility you’ll have with your given mix of livestock species in the system.